‘Second Earth’ exoplanet found right under our noses – just four light years away

Proxima b is a likely target for Starshot project

 

Artist’s impression of Proxima b and Proxima Centauri [Photo credit: ESO/M. Kornmesser]

Rumours that a terrestrial planet orbiting Proxima Centauri – the Sun’s closest neighbour – may be Earth-like have been confirmed today in a paper published in Nature.

The possibility that extraterrestrial life may exist next door was first reported last week in Der Spiegel, a German weekly news magazine.

Excitement bubbled over and the European Southern Observatory refused to confirm or deny the rumours, as it wanted to keep the research under wraps. But it eventually gave in, and announced that all details would be revealed at the end of August.

Tantalising evidence shows the candidate planet, known as Proxima b, may be small and rocky and lies in the habitable zone around its star – just like Earth.

Proxima b’s equilibrium temperature is within the range where water may be in liquid form on its surface, the researchers believe.

It orbits around Proxima Centauri, a red-dwarf located only 4.25 light years away in the closest star system, Alpha Centauri. It’s much closer to its star than the Earth is to the Sun at 0.05 astronomical units away, so a year only lasts 11.2 days.

How Earth-like is Proxima b?

Although the signs are promising, it’s completely hypothetical that Proxima b is Earth-like, the researchers said.

Infographic compares the orbit of Proxima b around Proxima Centauri with the same region of the Solar System [Photo credit: ESO/M. Kornmesser/G. Coleman]

Professor Hugh Jones, who was part of the large team analysing data from Proxima b and a physics lecturer at the University of Hertfordshire, told The Register: “Saying it’s more Earth-like than just its mass is speculative. It’s exciting because it’s the first time anybody has found a planet around the closest stars. We have been looking for ages.”

Sixteen years ago, researchers first spotted a signal that Proxima Centauri could be harbouring a planet. It took a while for confirmation because of the faint signal, Jones said.

Proxima Centauri is a faint star with a luminosity much lower than the Sun. Its surface temperature is 3,050 kelvin, as compared to the Sun’s 5,777 kelvin. Researchers used Doppler spectroscopy to measure changes in the velocity of the star caused by a gravitationally bound body that was orbiting around it.

The Doppler method is an effective way of detecting exoplanets, but it doesn’t give much information about the planet itself. Many properties, including Proxima b’s radius, are currently unknown.

Journey to Alpha Centauri

That doesn’t dampen the spirits of scientists and engineers working on the Breakthrough Starshot project, however.

Starshot was launched in April 2016 by Russian billionaire Yuri Milner and acclaimed physicist Stephen Hawking. The project aims to send tiny “nanocrafts” to the Alpha Centauri system, about 25 trillion miles away, at 15 to 20 per cent of the speed of light.

Speaking about the research, Professor Avi Loeb, Chairman of the Breakthrough Starshot advisory committee and researcher at Harvard University, told The Register: “We will celebrate this important discovery within the Starshot team.”

“The discovery of the habitable planet around the nearest star, Proxima Centauri, is strategically important for motivating the Breakthrough Starshot initiative, since it provides an obvious target for a flyby mission.

“A spacecraft equipped with a camera and various filters could take color images of the planet and infer whether it is green (harboring life as we know it), blue (with water oceans on its surface) or just brown (dry rock),” Loeb said.

The bright star is Alpha Centauri AB and Proxima Centauri is the fainter red dwarf star [Photo credit: Digitized Sky Survey 2, Acknowledgement: Davide De Martin/Mahdi Zamani]

Proxima b has another property that increases its chances of harbouring life, Loeb, who was uninvolved in the research, said.

“Low-mass stars burn nuclear fuel at a slower rate, so they are more likely to live longer. Proxima Centauri is smaller than our Sun and will live about a thousand times longer. This means that any life on the planet has a longer time to develop and survive,” Loeb told The Register.

“Hence, a habitable rocky planet around Proxima would be the most natural location to where our civilization could aspire to move after the Sun will die, five billion years from now.”

The prospect of nanobots venturing to Proxima b to take photos is still very far away, and with current technology it’s still difficult to resolve Proxima b from its star. But with better telescopes and sensitive instruments being built in the next decade, the close proximity of Proxima b gives researchers their best fighting chance yet of looking out for extraterrestrial life.

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Did our sun steal ‘Planet 9’ from another star?

There are eight planets in our solar system, and have been officially ever since Pluto was reclassified as a dwarf planet in 2006. But what if there was a ninth planet, billions of miles past Neptune?

Earlier this year, researchers from CalTech announced that they had found signs of the planet, which is referred to a “Planet 9,” through modeling and computer simulations. If a ninth planet were out there, it would be a big one— ten times the mass of Earth— and very, very far away, completing just one orbit around the sun as slowly as perhaps every 10,000 to 20,000 years.

Related: Scientists may have just found a ninth planet and it’s massive

Now, scientists from Lund University in Sweden have used computer simulations to propose a new theory about how Planet 9— if it exists— came to be a member of the solar system. They propose that it was stolen by our sun from another star about 4.5 billion years ago.

“What we were arguing was that you could create this [Planet 9] around another star, and then the sun could capture it, in a close encounter,” Alexander Mustill, a researcher in the department of astronomy and theoretical physics at Lund University, explained in a video about the theory.

Related: NASA identifies 1,284 new exoplanets, most ever announced at once

“We argue that this is how you could put this planet on a wide orbit around the sun,” he added. “You first create it around another star, and then the sun captures it.”

The researchers argue that this would make this planet an exoplanet, which is the term scientists use to describe planets in other star systems beyond our own. Just last month, NASA announced that they had added over 1,200 new exoplanets to the official roster, all of them discoveries from the Kepler spacecraft that had been validated through a new statistical method.

Related: Planet discovery fuels interest in mythical world of deep space

“It’s very exciting to this that there might be an extrasolar planet in our own solar system,” Mustill said.

The study proposing the new theory about Planet 9 was published online in the Monthly Notices of the Royal Astronomical Society in April.

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Three newly discovered Earth-sized planets may be prime spot to hunt alien life

The artist’s impression provided by European Southern Observatory on May 2, 2016 shows an imagined view from the surface one of the three planets orbiting an ultracool dwarf star just 40 light-years from Earth that were discovered using the TRAPPIST telescope at ESO’s La Silla Observatory. (ESO/M. Kornmesser via AP)

CAPE CANAVERAL, Fla. –  Astronomers searching for life beyond our solar system may need to look no farther than a little, feeble nearby star.

A Belgian-led team reported Monday that it’s discovered three Earth-sized planets orbiting an ultra-cool dwarf star less than 40 light-years away. It’s the first time planets have been found around this type of star — and it opens up new, rich territory in the search for extraterrestrial life.

Because this star is so close and so faint, astronomers can study the atmospheres of these three temperate exoplanets and, eventually, hunt for signs of possible life. They’re already making atmospheric observations, in fact, using NASA’s Spitzer Space Telescope. The Hubble Space Telescope will join in next week.

Altogether, it’s a “winning combination” for seeking chemical traces of life outside our solar system, said Massachusetts Institute of Technology researcher Julien de Wit, a co-author of the study, released by the journal Nature.

The star in question — named Trappist-1 after the Belgian telescope in Chile that made the discovery — is barely the size of Jupiter and located in the constellation Aquarius.

Other exoplanet searches have targeted bigger, brighter stars more like our sun, but the starlight in these cases can be so bright that it washes out the signatures of planets. By comparison, cool dwarf stars that emit infrared light, like Trappist-1, make it easier to spot potential worlds.

University of Liege astronomers in Belgium — lead study authors Michael Gillon and Emmanuel Jehin — built the Trappist telescope to observe 60 of the nearest ultra-cool dwarf stars. The risky effort paid off, de Wit noted in an email.

“Systems around these tiny stars are the only places where we can detect life on an Earth-sized exoplanet with our current technology,” Gillon said in a statement. “So if we want to find life elsewhere in the universe, this is where we should start to look.”

The two inner exoplanets take between 1.5 and 2.4 days to orbit the Trappist-1 star. The precise orbit time of the third planet is not known, but it falls somewhere between 4.5 days and 73 days. That puts the planets 20 times to 100 times closer to their star than Earth is to our sun, Gillon noted. The setup is more similar in scale to Jupiter’s moons than to our solar system, he added.

Although the two innermost planets are very close to the star, it showers them with only a few times the amount of energy that Earth receives from our own sun. The third exoplanet farther out may receive significantly less of such radiation than Earth does.

The astronomers speculate the two inner exoplanets may have pockets where life may exist, while the third exoplanet actually might fall within the habitable zone — real estate located at just the right distance from a star in order to harbor water and, possibly, life.

Spitzer and Hubble should answer whether the exoplanets have large and clear atmospheres, according to de Wit. They also might be able to detect water and methane, if molecules are present.

Future observatories, including NASA’s James Web Space Telescope set to launch in 2018, should unearth even more details.

Gillon and his colleagues identified the three exoplanets by observing regular dips in the infrared signals emanating from the Trappist-1 star, some 36 light-years away. A single light-year represents about 6 trillion miles.

The astronomers conducted the survey last year using the Transiting Planets and Planetesimals Small Telescope, or Trappist. It’s considered a prototype for a more expansive European project that will widen the search for potentially habitable worlds to 500 ultra-cool stars. This upcoming project is dubbed Speculoos — short for Search for Habitable Planets Eclipsing Ultra-Cool Stars.

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There’s a ninth planet out there – now we just need to find it

Mathematics suggests hidden gas giant in solar system

The truth is out there; way, way out there (source: CalTech/R.Hurt)

Pic Scientists at CalTech claim to have found proof that there is a ninth planet in the solar system, using computer modeling and historical astronomy data.

The new planet has a mass about 10 times that of Earth and has a very eccentric path around our Sun, making one complete orbit every 10,000 or 20,000 years and travelling 200 times further from the Sun than our orbit. The planet hasn’t been seen, but can be determined to exist based on its effect on objects in the Kuiper Belt that encircles our solar system.

“This would be a real ninth planet,” said Mike Brown, the Richard and Barbara Rosenberg Professor of Planetary Astronomy at the California Institute of Technology. “There have only been two true planets discovered since ancient times, and this would be a third. It’s a pretty substantial chunk of our solar system that’s still out there to be found, which is pretty exciting.”

That’s true, thanks to our modern definition of what a planet is. We’ve known about all the planets as far out as Saturn since before telescopes, and the advent of optics led to the discovery of Uranus back in 1781.

The existence of Neptune, like the new ninth planet, was proved mathematically before it was identified in 1846 based on the erratic movement of Uranus. Pluto was also proved mathematically to exist but it was nearly 100 years later before it was confirmed, and then demoted to dwarf planet status in an infamous 2006 astronomers’ vote.

There’s no fear of that in the case of the new ninth planet – it’s massive enough to cause objects in the Kuiper Belt to move in such a predictable fashion that Brown and his associate Konstantin Batygin estimate there’s only a 0.07 per cent possibility that they are mistaken about its existence.

In a paper published in the latest issue of The Astronomical Journal, the duo detail how they came to find the planet when a student of Brown’s noticed that 13 large objects in the Kuiper Belt were behaving oddly, as though they were being influenced by a much larger body.

Brown and Batygin spent the next 18 months building up complex mathematical simulations of what could be causing the movement and running them through a computer model. Brown supplied the astronomical data and Batygin applied physics to see what could be going on.

“I would bring in some of these observational aspects; he would come back with arguments from theory, and we would push each other. I don’t think the discovery would have happened without that back and forth,” said Brown. “It was perhaps the most fun year of working on a problem in the solar system that I’ve ever had.”

At first the two considered that maybe other Kuiper Belt objects were causing the orbital anomalies, but the sums didn’t add up – the Belt would have had to have 100 times the mass we understand it has. So that left the influence of a planet, and one that was orbiting the Sun at right angles to the orbits of other planets.

“Your natural response is ‘This orbital geometry can’t be right. This can’t be stable over the long term because, after all, this would cause the planet and these objects to meet and eventually collide,'” said Batygin. “Still, I was very skeptical. I had never seen anything like this in celestial mechanics.”

In order for the theory to be accurate, there would have to be other Kuiper Belt objects on a similar 90-degree trajectory. After three years of looking, the two found four largish objects that did just that.

“We plotted up the positions of those objects and their orbits, and they matched the simulations exactly,” says Brown. “When we found that, my jaw sort of hit the floor.”

Planets are supposed to form from the disk of matter that surrounds a young star, but the unusual orbit suggests that while the ninth planet might have started that way, it got knocked out of alignment, possibly by a major object like Jupiter, and sent on a new orbital trajectory.

Despite orbiting so far away from the Sun, planet nine should still be visible using our most powerful telescopes, and may have been picked up on star surveys and not recognized for what it is. The hunt is now on to be the first to get a clear sighting.

“I would love to find it,” says Brown. “But I’d also be perfectly happy if someone else found it. That is why we’re publishing this paper. We hope that other people are going to get inspired and start searching.”

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Wolf 1061 exoplanet: ‘Super-Earth’ discovered only 14 light-years away

Alien life could be closer to us than previously thought. Scientists have just discovered the nearest habitable planet to Earth.

The new world is one of three surrounding a red dwarf star called Wolf 1061, which is just 14 light years away. It was detected by scientists at the University of New South Wales (UNSW) in Australia.

All three planets have the potential to be solid and rocky, but only Wolf 1061c exists within the “Goldilocks zone” — a distance from the star (much smaller and cooler than our sun) that is not too hot and not too cold for liquid water.

“This rare discovery is incredibly exciting,” UNSW’s Duncan Wright, who led the study, told CNN.

“Other planets found that are habitable are not nearly this close to Earth. Because of the close proximity of this planet to us, there is good opportunity to find out more about it.”

“The close proximity of the planets around Wolf 1061 means there is a good chance these planets may pass across the face of the star,” UNSW team member Rob Wittenmyer said in an earlier statement.

“If they do, then it may be possible to study the atmospheres of these planets in future to see whether they would be conducive to life.”

Space surrounding red dwarf star Wolf 1061.

NASA has confirmed more than 1,870 exoplanets — worlds outside our solar system. But this discovery is particularly important because Wolf 1061c is both habitable and close to our solar system.

New planetary find “best chance for life outside our solar system”

Astronomers have made two new planetary discoveries that they claim expand the known boundaries of our solar system — and they may be the biggest breakthroughs in the search for alien life.

The two finds, one planet at the edge of our solar system and one just beyond, have both been hailed as major scientific advances.

Commenting on one of the planets, Brad Tucker, an astronomer from Mount Stromlo Observatory in Canberra, Australia who was not involved in the research, said it “probably gives us the best chance for life outside our solar system right now.”

“One of the goals of astronomy and astrophysics and finding these planets is firstly to really find another Earth,” he added. “And part of the reason of finding another Earth is that we ultimately do want to find life in the universe. It’s a question that weighs on everyone’s mind.

Lying on the edge of our solar system, a new, rocky planet close to the size of Earth and named GJ 1132b, is the discovery that holds the most potential for finding new life to date, according to astronomers.

The scientists who discovered it it said its small size and proximity — it’s three times closer than any other similar object found orbiting a star — “bodes well for studies of the planet’s atmosphere,” according to their report in the journal, Nature.

“GJ 1132b (is) arguably the most important planet ever found outside the solar system,” Drake Deming, an astronomer at the University of Maryland said in an accompanying letter in the journal. He added that it’s proximity will “allow astronomers to study the planet with unprecedented fidelity.”

Found moving across a “red dwarf” star that is only a fifth of the size of the world’s sun, the planet has a radius only 16% larger than Earth’s, and has surface temperatures that reach 260 degrees Celsius. Although that’s too hot to retain liquid water or sustain life as we know it, Tucker said it was cool enough to support some of the basic building blocks of life, and possibly support life forms like bacteria.

“We haven’t even found anything close to this so far,” he said.

“It’s more habitable, it’s less harsh and this gives us a good strong chance of actually finding life or something as opposed to the other Earth-like planets found to date.”

The planet also completes an orbit or passes its star once every 1.6 days, providing more opportunities for research and measurement than any other planet has provided to date, Tucker added.

“By being able to find evidence of these smaller, more inner planets, these rocky planets that we have in our solar system, we’re really realizing that the planets are probably in the trillions in our galaxy alone.”

http://www.cnn.com/2015/11/12/world/solar-system-discoveries-earth/index.html#

NASA stuns with new image of ‘Pillars of Creation’

New “Pillars of Creation” Hubble photo. (NASA)

(CNN)NASA has come out with a new image that could become one of its most iconic ever.

The Hubble Space Telescope revisited the so-called “Pillars of Creation,” which the space agency describes as “three giant columns of cold gas bathed in the scorching ultraviolet light from a cluster of young, massive stars in a small region of the Eagle Nebula, or M16.”

The previous photo of these pillars, taken in 1995, went on to stand out from all the rest of NASA’s space images, the agency said. “The Hubble image is so popular that it has appeared in movies and television shows, on T-shirts and pillows, and even on a postage stamp.”

 The old and new images, side by side

In celebration of the telescope’s upcoming 25th anniversary in April, Hubble returned to the pillars — and this time with the latest high-definition tools.

The new sharper and wider image was taken “in near-infrared light, as well as visible light,” NASA said. “The infrared view transforms the pillars into eerie, wispy silhouettes seen against a background of myriad stars. That’s because the infrared light penetrates much of the gas and dust, except for the densest regions of the pillars. Newborn stars can be seen hidden away inside the pillars.”

In 1995, the captured image gave insight into star formation. “Nebulous star-forming regions like M16 are the interstellar neon signs that say, ‘We just made a bunch of massive stars here,'” said Paul Scowen of Arizona State University, who helped lead the original observations, in a post on NASA’s website.

The new image “hints” that these columns “are also pillars of destruction,” NASA said.

“The ghostly bluish haze around the dense edges of the pillars is material getting heated up and evaporating away into space,” said Scowen. “We have caught these pillars at a very unique and short-lived moment in their evolution.”

First potentially habitable Earth-sized planet confirmed: It may have liquid water

The artist’s concept depicts Kepler-186f, the first validated Earth-size planet orbiting a distant star in the habitable zone—a range of distances from a star where liquid water might pool on the surface of an orbiting planet. The discovery of Kepler-186f confirms that Earth-size planets exist in the habitable zone of other stars and signals a significant step closer to finding a world similar to Earth. The artistic concept of Kepler-186f is the result of scientists and artists collaborating to help imagine the appearance of these distant worlds. (Danielle Futselaar)

The first Earth-sized exoplanet orbiting within the habitable zone of another star has been confirmed by observations with both the W. M. Keck Observatory and the Gemini Observatory. The initial discovery, made by NASA’s Kepler Space Telescope, is one of a handful of smaller planets found by Kepler and verified using large ground-based telescopes. It also confirms that Earth-sized planets do exist in the habitable zone of other stars.

“What makes this finding particularly compelling is that this Earth-sized planet, one of five orbiting this star, which is cooler than the Sun, resides in a temperate region where water could exist in liquid form,” says Elisa Quintana of the SETI Institute and NASA Ames Research Center who led the paper published in the current issue of the journal Science. The region in which this planet orbits its star is called the habitable zone, as it is thought that life would most likely form on planets with liquid water.

Steve Howell, Kepler’s Project Scientist and a co-author on the paper, adds that neither Kepler (nor any telescope) is currently able to directly spot an exoplanet of this size and proximity to its host star. “However, what we can do is eliminate essentially all other possibilities so that the validity of these planets is really the only viable option.”

With such a small host star, the team employed a technique that eliminated the possibility that either a background star or a stellar companion could be mimicking what Kepler detected. To do this, the team obtained extremely high spatial resolution observations from the eight-meter Gemini North telescope on Mauna Kea in Hawai`i using a technique called speckle imaging, as well as adaptive optics (AO) observations from the ten-meter Keck II telescope, Gemini’s neighbor on Mauna Kea. Together, these data allowed the team to rule out sources close enough to the star’s line-of-sight to confound the Kepler evidence, and conclude that Kepler’s detected signal has to be from a small planet transiting its host star.

The diagram compares the planets of the inner solar system to Kepler-186, a five-planet system about 500 light-years from Earth in the constellation Cygnus. The five planets of Kepler-186 orbit a star classified as a M1 dwarf, measuring half the size and mass of the sun. The Kepler-186 system is home to Kepler-186f, the first validated Earth-size planet orbiting a distant star in the habitable zone—a range of distances from a star where liquid water might pool on the surface of an orbiting planet. The discovery of Kepler-186f confirms that Earth-size planets exist in the habitable zone of other stars and signals a significant step closer to finding a world similar to Earth. Kepler-186f is less than ten percent larger than Earth in size, but its mass and composition are not known. Kepler-186f orbits its star once every 130-days and receives one-third the heat energy that Earth does from the sun, placing it near the outer edge of the habitable zone. The inner four companion planets all measure less than fifty percent the size of Earth. Kepler-186b, Kepler-186c, Kepler-186d, and Kepler-186e, orbit every three, seven, 13, and 22 days, respectively, making them very hot and inhospitable for life as we know it. The Kepler space telescope, which simultaneously and continuously measured the brightness of more than 150,000 stars, is NASA’s first mission capable of detecting Earth-size planets around stars like our sun. Kepler does not directly image the planets it detects. The space telescope infers their existence by the amount of starlight blocked when the orbiting planet passes in front of a distant star from the vantage point of the observer. The artistic concept of Kepler-186f is the result of scientists and artists collaborating to help imagine the appearance of these distant Credit: (NASA Ames/SETI Institute/JPL-CalTech.)

“The Keck and Gemini data are two key pieces of this puzzle,” says Quintana. “Without these complementary observations we wouldn’t have been able to confirm this Earth-sized planet.”

The Gemini “speckle” data directly imaged the system to within about 400 million miles (about 4 AU, approximately equal to the orbit of Jupiter in our solar system) of the host star and confirmed that there were no other stellar size objects orbiting within this radius from the star. Augmenting this, the Keck AO observations probed a larger region around the star but to fainter limits. According to Quintana,

“These Earth-sized planets are extremely hard to detect and confirm, and now that we’ve found one, we want to search for more. Gemini and Keck will no doubt play a large role in these endeavors.”

The host star, Kepler-186, is an M1-type dwarf star relatively close to our solar system, at about 500 light years and is in the constellation of Cygnus. The star is very dim, being over half a million times fainter than the faintest stars we can see with the naked eye. Five small planets have been found orbiting this star, four of which are in very short-period orbits and are very hot. The planet designated Kepler-186f, however, is earth-sized and orbits within the star’s habitable zone. The Kepler evidence for this planetary system comes from the detection of planetary transits. These transits can be thought of as tiny eclipses of the host star by a planet (or planets) as seen from the Earth. When such planets block part of the star’s light, its total brightness diminishes. Kepler detects that as a variation in the star’s total light output and evidence for planets. So far more than 3,800 possible planets have been detected by this technique with Kepler.

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New Exoplanet Hunter Directly Images Alien Worlds

Gemini Planet Imager’s ‘first light’ image of Beta Pictoris b, an exoplanet orbiting the star Beta Pictoris.

A new instrument, attached to one of the most powerful telescopes in the world, has opened its infrared eye for the first time, taking snapshots of a nearby planet orbiting another star and a ring of proto-planetary stellar dust.

The sophisticated car-sized instrument, called the Gemini Planet Imager (GPI), is attached to the 8-meter Gemini South telescope in Chile and represents a new era in exoplanetary discovery. The GPI, which has been in development since 2003, is capable of not only resolving the dim light from an exoplanet orbiting close to its parent star; it can also analyze the planet’s atmospheric composition and temperature.

GALLERY: The Most Horrific Alien Planets In Our Galaxy

The majority of ground-based exoplanet surveys watch for stars’ “wobbles” to betray the gravitational presence of massive exoplanets in orbit — known as the “radial velocity technique.” Another powerful technique for discovering smaller exoplanets in tight orbits around their star is employed by NASA’s Kepler space telescope. As an exoplanet passes in front of its host star, a small dip in brightness can be detected by Kepler’s sensitive optics – this is known as a “transit.”

Other methods for exoplanetary detection are possible (such as microlensing), but the “Holy Grail” for astronomers is to use a powerful telescope to directly image star systems, picking out tiny dots of light in orbit. This feat has been achieved a handful of times (most notably the 2008 Hubble and Keck/Gemini announcements of directly imaging exoplanets around the stars Fomalhaut and HR 8799) its wholesale use as an effective exoplanet-hunting tool has been limited by technology, a limit that the GPI has now dramatically lifted.

PHOTOS: Herschel’s Coolest Infrared Hotshots

Through the ingenious combination of adaptive optics — a laser system used on some observatories that can actively counteract the blurring effects of turbulence in the Earth’s atmosphere — and an active obscuring coronagraph perfectly covering the star (to counteract the glaring effect of the starlight), GPI has the power to distinguish star from exoplanet to unparalleled precision.

“Most planets that we know about to date are only known because of indirect methods that tell us a planet is there, a bit about its orbit and mass, but not much else,” said Bruce Macintosh of the Lawrence Livermore National Laboratory, who led the team that developed GPI. “With GPI we directly image planets around stars — it’s a bit like being able to dissect the system and really dive into the planet’s atmospheric makeup and characteristics.”

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4.5 billion ‘alien Earths’ may populate Milky Way

This artist’s conception shows a hypothetical habitable planet with two moons orbiting a red dwarf star. Astronomers have found that 6 percent of all red dwarf stars have an Earth-sized planet in the habitable zone, which is warm enough for liq (David A. Aguilar (CfA))

Billions of Earth-like alien planets likely reside in our Milky Way galaxy, and the nearest such world may be just a stone’s throw away in the cosmic scheme of things, a new study reports.

Astronomers have calculated that 6 percent of the galaxy’s 75 billion or so red dwarfs — stars smaller and dimmer than the Earth’s own sun — probably host habitable, roughly Earth-size planets. That works out to at least 4.5 billion such “alien Earths,” the closest of which might be found a mere dozen light-years away, researchers said.

“We thought we would have to search vast distances to find an Earth-like planet,” study lead author Courtney Dressing, of the Harvard-Smithsonian Center for Astrophysics (CfA), said in a statement. “Now we realize another Earth is probably in our own backyard, waiting to be spotted.”

Kepler’s keen eye
Dressing and her team analyzed data gathered by NASA’s prolific Kepler space telescope, which is staring continuously at more than 150,000 target stars. Kepler spots alien planets by flagging the tiny brightness dips caused when the planets transit, or cross the face of, their stars from the instrument’s perspective. [Gallery: A World of Kepler Planets]

‘Another Earth is probably in our own backyard, waiting to be spotted.’

– Courtney Dressing, of the Harvard-Smithsonian Center for Astrophysics

Kepler has detected 2,740 exoplanet candidates since its March 2009 launch. Follow-up observations have confirmed only 105 of these possibilities to date, but mission scientists estimate that more than 90 percent will end up being the real deal.

In the new study, Dressing and her colleagues re-analyzed the red dwarfs in Kepler’s field of view and found that nearly all are smaller and cooler than previously thought.

This new information bears strongly on the search for Earth-like alien planets, since roughly 75 percent of the galaxy’s 100 billion or so stars are red dwarfs.

Further, scientists determine the sizes of transiting exoplanets by comparison to their parent stars, based on how much of the stars’ disks the planets blot out when transitting. So a reduction in a star’s calculated size brings a planet’s size down, too — in some cases, perhaps into the realm of rocky worlds with a solid, potentially life-supporting surface.

And the size and location of a star’s “habitable zone,” the range of distances that could support the existence of liquid water on a planet’s surface, are strongly tied to stellar brightness and temperature.

Re-analzying the data
The researchers determined that 95 Kepler exoplanet candidates orbit red dwarfs. Using this information and their newly calculated stellar (and planetary) profiles, the team calculated that about 60 percent of red dwarfs likely host worlds smaller than Neptune.

Dressing and her colleagues then determined that Kepler has spotted three roughly Earth-size exoplanet candidates in the habitable zones of their parent red dwarfs.

One of these worlds is Kepler Object of Interest (KOI) 1422.02. This candidate’s newly calculated size is 90 percent that of Earth, and it circles its star every 20 days. If the planet (and these characteristics) are confirmed, KOI 1422.02 may be the first “alien Earth” ever discovered.

The other two candidates are KOI 2626.01, another potential Earth twin that’s 1.4 times bigger than Earth and has a 38-day orbit; and KOI 854.01, a world 1.7 times the size of Earth with a 56-day orbit.

All three candidates are located between 300 and 600 light-years from Earth and circle stars with surface temperatures between 5,700 and 5,900 degrees Fahrenheit, researchers said. (For comparison, the Earth’s sun has a surface temperature of about 10,000 degrees Fahrenheit.)

Billions of Earth-like planets
The team further determined that about 6 percent of the Milky Way’s red dwarfs should harbor roughly Earth-size planets in their habitable zones, meaning that at least 4.5 billion such worlds may be scattered throughout our galaxy.

“We now know the rate of occurrence of habitable planets around the most common stars in our galaxy,” co-author David Charbonneau, also of CfA, said in a statement. “That rate implies that it will be significantly easier to search for life beyond the solar system than we previously thought.” [9 Exoplanets That Could Host Alien Life]

That search may bear fruit right in Earth’s backyard, researchers said.

“According to our analysis, the closest Earth-like planet is likely within 13 light-years, which is right next door in terms of astronomical distances,” Dressing told SPACE.com via email.

“The knowledge that another an Earth-like planet might be so close is incredibly exciting and bodes well for the next generation of missions designed to detect nearby Earth-like planets,” she added. “Once we find nearby Earth-like planets, astronomers are eager to study them in detail with the James Webb Space Telescope and proposed extremely large ground-based telescopes like the Giant Magellan Telescope.”

Red dwarfs are also longer-lived than stars like the sun, suggesting that some planets in red dwarf habitable zones may harbor life that’s been around a lot longer than that on Earth, which first took root about 3.8 billion years ago.

“We might find an Earth that’s 10 billion years old,” Charbonneau said.

The nearest red dwarf is Proxima Centauri, part of the three-star Alpha Centauri system that’s just 4.3 light-years or so from Earth. Late last year, astronomers announced the discovery of an Earth-size planet orbiting the system’s Alpha Centauri B, but it’s far too hot to host life as we know it.

Scientists have also detected five planetary candidates circling the star Tau Ceti, which lies 11.9 light-years away. Two of these potential planets may reside in the habitable zone, but they are at least 4.3 and 6.6 times as massive as Earth, scientists say.

The new study will be published in The Astrophysical Journal.